Objective According to the distr ibution of low selenium areas, low nutrition state of the residents and the affecting cartilage growth and articular cartilage of Kashin-Beck Disease (KBD), the chondrocyte differen tiation and differential expression of collagen types i, II and X in articular cartilage from Chinese mini-pigs treated with low selenium were investigated in order to gain in sight in to the effects of these condition son chondrocyte differen tiation in KBD cartilage. Me thods Eleven male juvenile mini-pigs, aged from 4 weeks to 6 weeks after birth, were divided in to 3 groups. The Secontent in the diet of the "low Se" group was 0.035mg/kg diet, and 0.175mg/kg diet in the control. For Se-supplemented group 0.390mg Na2SeO3/kg diet was added. The con tent of Sein blood was assayed at the beginning and at the end of each experiment. Samples of articular cartilage were taken from the right femur condylus, and collagen types I, II and "in articular cartilage were analyzed by immunohistochem istry and in situ hybridization. Results ①All cartilage samples from juven ilem in i-pigs fed with low selenium dietrevealed areduction in type "collagen mRNA expression in the hypertrophic chondrocytes as shown by in situ hybridization, and reduced type "collagen depos ition in the lower hypertrophic zone as shown by immunohistochem istry. ②Addition of selenium to the dietrestored the type" collagen to normal level. ③Type collagen was evenly distr ibuted over the entire articular cartilage in all experimental and controlgroups. Type collagen mRNA signals weremost prominent in the upper articular layer as well as in the hypertrophic zone in all groups. Type collagen express ion was restricted to the zone of endochondraloss if ication in all experimental groups and the control. Conclusion　Low selen ium has an down-regulatoryrole on the syn thes is and deposition of collagen type "in hypertrophic chondrocytes in articular cartilage of mini-pigs. Supplement of the low Sediet with additional Serestored the signals of collagen type" to normal levels. These findings indicate that selenium deficiency may disturb chondrocyte differen tiation to hypertrophic cells in the growth plate, and worthy to be investigated further.